De Havilland Canada Twin Otter

Design and development

Development of the aircraft began in 1964, with the first flight on 20 May 1965. A twin-engine replacement for the single-engine DHC-3 Otter retaining the DHC-3's STOL qualities, its design features included double-slotted trailing-edge flaps and ailerons that work in unison with the flaps to boost STOL performance. The availability of the 550 shaft horsepower (410 kW) Pratt & Whitney Canada PT6A-20 turboprop in the early 1960s made the concept of a twin feasible. A DHC-3 Otter with its piston engine replaced with two PT6A-4 engines had already flown in 1963. It had been extensively modified for STOL research. To bush plane operators, the improved reliability of turboprop power and the improved performance of a twin-engine configuration made it an immediately popular alternative to the piston-powered Otter which had been flying since 1951.

The first six aircraft produced were designated Series 1, indicating that they were prototype aircraft. The initial production run consisted of Series 100 aircraft, serial numbers seven to 115 inclusive. In 1968, Series 200 production began with serial number 116. Changes made at the beginning of Series 200 production included improving the STOL performance, adding a longer nose that was equipped with a larger baggage compartment (except for aircraft fitted with floats), and fitting a larger door to the rear baggage compartment. All Series 1, 100, and 200 aircraft and their variants (110, 210) were fitted with the 550 shp (410 kW) PT6A-20 engines.

In 1969, the Series 300 was introduced, beginning with serial number 231. Both aircraft performance and payload were improved by fitting more powerful PT6A-27 engines. This was a 680 hp (510 kW) engine that was flat rated to 620 hp (460 kW) for use in the Series 300 Twin Otter. The Series 300 proved to be the most successful variant by far, with 614 Series 300 aircraft and their subvariants (Series 310 for United Kingdom operators, Series 320 for Australian operators, etc.) sold before production in Toronto by de Havilland Canada ended in 1988.

In 1972, its unit cost was US$680,000,

In 1976, a new -300 would have cost $700,000 ($3 million 31 years later) and is still worth more than $2.5 million in 2018 despite the -400 introduction, many years after the -300 production ceased. 844 had been produced by the time the first production end run ended in 1988.

New production

After Series 300 production ended, the remaining tooling was purchased by Viking Air of Victoria, British Columbia, which manufactures replacement parts for out-of-production de Havilland Canada aircraft. On 24 February 2006, Viking purchased the type certificates from Bombardier Aviation for all out-of-production de Havilland Canada aircraft (DHC-1 through DHC-7). The ownership of the certificates gives Viking the exclusive right to manufacture new aircraft.

On 17 July 2006, at the Farnborough Airshow, Viking Air announced its intention to offer a Series 400 Twin Otter. On 2 April 2007, Viking announced that with 27 orders and options in hand, it was restarting production of the Twin Otter, equipped with more powerful Pratt & Whitney Canada PT6A-34 engines. As of November 2007, 40 firm orders and 10 options had been taken and a new final assembly plant was established in Calgary, Alberta. Zimex Aviation of Switzerland received the first new production aircraft, serial number 845, in July 2010. By mid-2014, Viking had built 55 new aircraft at its Calgary facility. The production rate as of summer 2014 was about 24 aircraft per year. In April 2015, Viking announced a reduction of the production rate to 18 aircraft per year. On 17 June 2015, Viking announced a partnership with a Chinese firm, Reignwood Aviation Group; the group would purchase 50 aircraft and become the exclusive supplier of new Series 400 Twin Otters in China.

Major changes introduced with the Series 400 include Honeywell Primus Apex fully integrated avionics, deletion of the AC electrical system, modernization of the electrical and lighting systems, and use of composites for non load-bearing structures such as doors.

The 100th Series 400 Twin Otter (MSN 944) was displayed at the July 2017 EAA AirVenture Oshkosh. At the time 38% were operated as regional airliners, 31% were in military aviation use, 26% in industrial support and 5% were in private air charter. Seventy were on regular landing gear wheels, 18 were configured as straight or amphibious floatplanes, 10 had tundra tires and two had wheel skis.

In 2019, Viking started making plastic components for the Twin Otter by 3D printer to help reduce cost.

Twin Otter production was suspended in 2019 during the COVID-19 pandemic. In July 2022, DHC announced that it was reviewing the program and supply chain, with a decision on when to resume production expected "in the near future".

In 2023, its equipped price was $7.25M.

In June 2023, Viking, now operating as De Havilland Canada, started production of the new DHC-6 Classic 300-G.

On 20 March 2026, De Havilland Canada delivered its 1000th DHC-6 Twin Otter produced and delivered aircraft to SATENA, a regional government-owned airline of Colombia.